The broad, long-term objectives of this project are to develop approaches to prevent and treat respiratory diseases. We found that different T cells populations modulate inflammatory responses of murine mycoplasma pneumonia, and the factors that determine the type of T cell responses need to be understood. The role of dendritic cells (DCs) and other antigen presenting cells, e.g. macrophages, in Mycoplasma disease is unknown, but because T cell responses in mycoplasma disease play such a critical role, DCs and macrophages likely impact on disease pathogenesis and influence the generation of protective immunity. We hypothesize that manipulating DC can predictably change the types and intensity of immune reactions in the lung against mycoplasma infection, and this will impact on the severity and resistance to disease. In addition, pulmonary macrophages may also impact on mycoplasma immunity, possibly through support of Th1-type responses. The impact of pulmonary DCs and macrophages activity needs to be compared. In this proposal, we will address the following questions: 1) Do changes in pulmonary DCs and macrophages from naive or mycoplasma-infected mice influence the ability to activate and modulate T cell differentiation and activation? 2) Can mycoplasma-antigen pulsed DCs or macrophages generate protective or immunopathologic responses against mycoplasma? 3) Can altering DC function with regulatory cytokines influence pulmonary immune responses and mycoplasma respiratory disease? 4) Do the DCbeta-chemokines, ABCD-1 and ABCD-2 (TARC), play a role in pulmonary immunity against mycoplasma? The experimental design is as follows: 1) DCs and macrophages from the respiratory tracts of mycoplasma-infected mice will be evaluated for their ability activate in vitro and in vivo T cell responses against an unrelated antigen (OVA). 2) DCs and macrophages will be pulsed with mycoplasma antigen and their ability to generate resistance or immunopathology after intratracheal inoculation and subsequent challenge with mycoplasma will be determined. 3) DC will be treated in vitro with regulatory cytokines, IFNgamma, IL-12, IL-4 TGF-beta or IL-10, and pulsed with mycoplasma antigen, and their ability to generate resistance or immunopathology against mycoplasma will be determined by their intratracheal inoculation; and 4) T cells from lungs of Mycoplasma infected mice will be examined for expression of receptors for ABCD-1 and ABCD-2 and their ability to respond to these chemokines. Mice will be treated with neutralizing monoclonal antibodies to determine the role of ABCD-1 and ABCD-2 in protective immunity and immunopathologic responses against mycoplasma.